Refractory tube



FIG. 1 is a top perspective view of a refractory tube showing my new design;

FIG. 2 is a bottom perspective view;

FIG. 3 is a side elevational view taken from the left of FIG. 1, the side opposite being a mirror image thereof;

FIG. 4 is a top plan view;

FIG. 5 is a top perspective view of a second embodiment of the design of FIG. 1;

FIG. 6 is a bottom perspective view of FIG. 5;

FIG. 7 is a side elevational view taken from the left of FIG. 5, the side opposite being a mirror image therof. 

The ornamental design for a refractory tube, substantially as shown and described. 